In order to selectively control a plurality of load devices connected to a power line, it is generally necessary to extract a separate switch wire from each of the load devices.
When implementing a control system for the plurality of load devices at home, it is required to provide a number of switch wires in a control panel, and thus the system's installation and maintenance are difficult, and the expense is very heavy. In addition, when data of a specific frequency signal of a transmitting end is transmitted to a receiving end, there is no way for the transmitting end to check the state of the receiving end to which the data is transmitted, and check the operating states of the load devices. Thus, since there is no way for the transmitter to check the transmission states, it is difficult to check whether or not the plurality of load devices operates.
Meanwhile, most of currently available electronic products as load devices employ a remote controller based on light emission for controlling their operations, which allows the operations to be remotely controlled, thereby promoting the convenience of life.
With the development of technology, use of the remote controller will be wider. Particularly, the importance of the remote controller having a remote control function are being emphasized much more, with the development of technology toward home automation which allows control of electronic products located at home from the outside with no person inside the home. However, such a control method based on the remote controller has limitations in that the electronic product can be controlled only when it is located in a range of positions eachable by an optical signal of the remote controller.
On the other hand, a remote control method based on a pulse signal control, or a wireless control method based on a high frequency wave, has an advantage in that, since the operation is not performed with frequencies other than its inherent frequency, there is no risk of malfunction caused by other signals, but it has a disadvantage in that the cost is increased by the manufacturing and replacement of the system.